Commonly-owned U.S. Pat. Nos. 5,677,390, 5,686,538, 5,767,203, 5,852,131, 5,852,132, 5,916,978, 6,113,381, 6,207,765, 6,232,393, 6,232,408, 6,235,831, 6,235,844, 6,326,439, and 6,521,714 describe what is believed to be the best previously-published process technology for producing brominated styrenic polymers such as brominated polystyrene having the best properties of those of any previously-published brominated styrenic polymer. In this connection, the terms “brominated styrenic polymer” and “brominated polystyrene” as used in the specification and in the claims hereof refer to a brominated polymer produced by bromination of a pre-existing styrenic polymer such as polystyrene or a copolymer of styrene and at least one other vinyl aromatic monomer, as distinguished from an oligomer or polymer produced by oligomerization or polymerization of one or more brominated styrenic monomers, the properties of the latter oligomers or polymers typically being considerably different from brominated polystyrene in a number of respects.
The processes for preparing brominated polystyrenic polymers described in the foregoing commonly-owned patents teach the desirability of removing coproduct HBr that is usually found in the head space of the bromination reactor by passing such head space vapors into a scrubber, followed by providing a cook period for the bromination reaction mixture to allow bromination to continue to the desired extent, and then terminating the bromination reaction with a suitable aqueous medium. Such an operation is of economic importance since the HBr coproduct is of value either for use as HBr or for conversion to other commercially desirable products, such as bromine itself. In cases where bromine chloride is used as the brominating agent, HCl is formed as a coproduct.
Despite the excellence of such prior technology, new improvements, especially in the manner of conducting the processes, are always welcome. This invention is deemed to provide at least one such new improvement.